PROJECT SUMMARY/ABSTRACT Photochemical synthesis represents an exciting frontier for drug discovery and for biomedical research. The ability of small, structurally complex organic molecules to interact with biomolecules and perturb their behavior is at the heart of modern molecular medicine and chemical biology. The discovery of new drugs and biological probes with new properties, therefore, relies critically upon the synthesis of new molecules with unprecedented structures. Photochemistry has long been an underdeveloped technique in chemical synthesis, in part because the irradiation of organic molecules with light results in the generation of highly reactive, high-energy species that can react indiscriminately and unproductively. We are investigating the ways in which addition of various reagents to photochemical reactions can control these photogenerated intermediates in diverse ways. In this proposal, we describe two Specific Aims to study how these reagents can result in powerful new bond forming methods. Aim 1. We are exploring the ability of chiral catalysts to control the stereochemistry of photochemical reactions. Aim 2. We are exploring the ability of copper oxidants to enable the installation of functional groups onto simple unfunctionalized organic scaffolds. These methods enable chemical transformations that cannot otherwise be accomplished using conventional, non-photochemical technologies. Thus, we expect that the results of our research will have significant impacts both in fundamental academic chemical research and on the ability of biomedical scientists to synthesize and discover the next generation of life-saving drugs.